The goal of the proposed work is to elucidate the biological process of aging in exocrine secretory cells. The immediate objectives of the proposed study are to determine whether or not age-related changes occur in these cells with respect to the ability to form secretory products. Using the acinar cells of the rat parotid gland as a model system, studies are done to determine what age-related changes occur in synthesis, processing and packaging of secretory proteins, and what structural alterations occur in the gland in relation to the histological and fine structural appearances. The areas of study planned for the coming year are the investigations of 1) the rate of amylase restitution and 3H-leucine incorporation following isoproterenol stimulation, 2) intracellular processing of secretory proteins and 3) morphometric analyses of the gland at the light and electron microscope level.